1. Field of the Invention
This invention relates to a method of manufacturing a passage tube through which plasma producing gas passes and is irradiated by an ultraviolet ray.
2. Description of Related Art
Recently, a plasma treating apparatus that has high treating efficiency and is capable of conducting work with high precision has frequently been used with the rapid advance for the formation of fine semiconductor patterns. For example, plasma is used for forming a fine pattern by forming a thin film on a substrate to be treated and then selectively etching the thin film. When the plasma is produced, gas is ionized to produce a radical of gas constituting molecule and the resulting radical is impinged onto the substrate to promote a reaction. As the radical, there are ion radicals and neutral radicals, both of which are very active and effectively promote vapor phase growth and dry etching.
Quartz is used as the material for the passage tube for passing the plasma producing gas. Meanwhile, when radicals of a halide gas are used, which are particularly corrosive, the passage tube becomes corroded and must be replaced frequently. Although quartz is high in ultraviolet translucency, the transparency of quartz is particularly lost by the corrosion through plasma of corrosive halide gas and hence it is easy to lower the efficiency of ultraviolet translucency.
The inventors have made studies with respect to the material of the passage tube and found that a specified translucent alumina has a very high corrosion resistance against plasma and a translucency for ultraviolet ray, which has been disclosed in Japanese Patent Application No. 8-149232. That is, the specification of this patent application disclosed that a tube body and a flange member for facilitating the arrangement of the tube body to a plasma treating apparatus are made from the translucent alumina and the tube body is jointed to a flange member.
However, it has been confirmed that there are technical problems in the process of manufacturing such a passage tube. That is, in order to manufacture this tube, it is required to fix the flange member to the tube body so as to make the flange member perpendicular to the tube body. In this case, it is further required to keep airtightness of the joint interface between the tube body and the flange member so as not to cause leakage of plasma producing gas from the joint interface. However, it is difficult to obtain such a joint body.